/*
 * Alloy Analyzer
 * Copyright (c) 2002 Massachusetts Institute of Technology
 *
 * The Alloy Analyzer is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * The Alloy Analyzer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Alloy Analyzer; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package alloy.transform;

import alloy.ast.ASTDepthFirstReplacer;
import alloy.ast.Decl;
import alloy.ast.Decls;
import alloy.ast.Expr;
import alloy.ast.ExprCastIntExpr;
import alloy.ast.Id;
import alloy.ast.Multiplicity;
import alloy.ast.Qualifiers;
import alloy.ast.SetMultExpr;
import alloy.ast.SumExpr;
import alloy.ast.SumIntExpr;
import alloy.ast.Variable;
import alloy.ast.VariableExpr;
import alloy.ast.Variables;
import alloy.semantic.AlreadyMappedException;
import alloy.semantic.LocalScope;

/**
 * <p>A visitor which SumExpr into SumIntExpr as follows:
 * sum expr ---> sum var : expr | int var 
 * <p>This desugaring is necessary since we do not atomizate
 * SumExprs
 */
public class DesugarSumExprVisitor extends ASTDepthFirstReplacer {
    private static final String VAR_NAME_BASE = "var";

    public DesugarSumExprVisitor() {}

    public Object visit(SumExpr sumExpr_) {
	

	// create the declaration, var : expr
	Expr expr = (Expr) sumExpr_.getExpr().copy();

	Variables vars = new Variables();
	Variable var = new Variable(Id.generateId(VAR_NAME_BASE));
	
	vars.addVariable(var);
	
	Decls decls = new Decls();

	decls.addDecl(new Decl(expr.getLocation(), new Qualifiers(), vars, 
			       new SetMultExpr(expr.getLocation(),
					       Multiplicity.NONE, expr)));

	// create the SumIntExpr, var : expr | int var
	VariableExpr varExpr = new VariableExpr((Variable) var.copy());
	varExpr.setType(expr.getType());

	LocalScope localScope = new LocalScope();
	try {
	    localScope.addMapping(var.getId().nodeString(), expr.getType());
	} catch (AlreadyMappedException ame) {
	    throw new RuntimeException("shouldn't reach here");
	}


	SumIntExpr sumIntExpr =  new SumIntExpr(sumExpr_.getLocation(),
						decls, new ExprCastIntExpr(varExpr));
	
	sumIntExpr.setLocalScope(localScope);

	return sumIntExpr;
	
    }


}
